• Nuclear Engineering and Technology
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• v.36 no.1
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• pp.24-35
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• 2004

In order to analyze the hydrogen distribution during a severe accident in the APR1400 containment, GASFLOW II was used. For the APR1400 NPP, a hydrogen mitigation system is considered from the design stage, but a fully time-dependent, three-dimensional analysis has not been performed yet. In this study GASFLOW code II is used for the three-dimensional analysis. The first step to analysis involving hydrogen behavior in a full containment with the GASLOW code is to generate a realistic geometry model, which includes nodalization and modeling of the internal structures such as walls, ceilings and equipment. Geometry modeling of the APR1400 is conducted using GUI program by overlapping the containment cut drawings in a graphical file format on the mesh view. The total number of mesh cells generated is 49,476. And the calculated free volume of the APR1400 containment by GASFLOW is almost the same as the value from the GOTHIC modeling. A hypothetical SB-LOCA scenario beyond design base accident was selected to analyze the hydrogen behavior with the hydrogen mitigation system. The source of hydrogen and steam for the GASFLOW II analysis is obtained from a MAAP calculation. Combustion pressure and temperature load possibilities within the compartments used in the GOTHIC analysis are studied based on the Sigma-Lambda criteria. Finally the effectiveness of HMS installed in the APR1400 containment is evaluated from the point of severe accident management

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.21 no.4
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• pp.293-299
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• 2003

In the future, the design of road should be convenient in using of high-technology information and it needs the design of alignment that is able to make the maximum vehicles inducement function appropriated for CNS(Car Navigation System). So it needs to analysis appropriately the alignment of road for the improvement design of road which is established and to make the design of road and the coordinate of the main points. Therefore, this research had acquired the road data by RTK-GPS to accurate the analysis of road alignment and compared with Total Station. As the result, we could acquire the design source of the road alignment using RTK-GPS. Also, it was estimated the accuracy after comparing the design with RTK-GPS coordinates. We made an analysis of the degree of slant or the ups and downs of surface. We made an analysis of three dimensional visual information which was included in GSIS concept and estimated the accuracy. Finally, we analyzed the earth volume calculation by comparing with Total Station.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4C
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• pp.254-264
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• 2011

In this paper, we propose two algorithm for improving the performance of wireless localization(Trilateration and Least Square) based on the range based approach method in indoor environment using RSSI for ranging distance. we propose a method to discriminate the case that has relatively large estimation errors in trilateration using Heron''s formula for the volume of a tetrahedron. And we propose the algorithm to process the discriminated types of distance using the absolute value calculated by Heron''s formula. In addition, we propose another algorithm for the case of which the number of anchor nodes larger than three. In this case, Residual Weighting Factor(RWGH) improves the performance of Least Square. However, RWGH requires many number of calculations. In this paper, we propose Iterative Weighted Centroid Algorithm(IWCA) that has better performance and less calculation than RWGH. We show the improvement of performance for two algorithms and the combination of these algorithm by using simulation results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.4
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• pp.771-779
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• 1989

Numerical analysis by SIMPLE algorithm has been performed to predict the characteristics of flow and heat transfer in channels between the printed circuit boards of an electronic cabinet. It is assumed that the electronic parts release uniform heat flux per unit axial length to the cooling air. The air flow between channels is assumed fully developed laminar, incompressible, and mixed convective. In this study, the electronic parts are mounted on both sides of the prinked circuit boards by two kinds of configuration such as the zig-zag and the symmetric one. The Rayleigh numbers ranging from 0 to 10$^{6}$ are considered to predict the characteristics of the main flow and the secondary flow occurred by natural convection, the temperature distribution in channel, the heat transfer rate from heated electronic parts and the increase of friction factor by natural convection. As the results of numerical calculation, several conclusions are drawn as follows. The influence of natural convection on the flow characteristics appears strong when the Rayleigh number is above 10$^{4}$. The main axial flow rate decreases by a half or more at the Rayleigh number of 10$^{6}$ . Although the friction factor increases as Rayleigh number increases, the increasing rate of heat transfer is higher than that of the friction factor. The cooling efficiency of the zig-zig-configuration is superior to that of the symmetric configuration at same Rayleigh number.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.1
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• pp.33-40
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• 2008

This paper proposes a sensorless drive method that estimates the rotor position by analysing Back EMF of single-phase Switched Reluctance motor (SRM). The rotor position information is necessary required, because SRM's torque is generated by exciting a stator winding according to rotor position. In order to detect the position of the rotor, the various rotor position sensors have been used. However, most of the position sensors not only increase the construction cost and the volume of the motor but also decrease reliability of driving system with environment. This paper proposed the method using the Back EMF to solve such problems. When a rotor and stator are overlapped, the Back EMF is sharply changed. By detecting this point, the rotor position can be estimated. Thus SRM is driven by turn on and turn off switches at the proper position through speed calculation. The validity of proposed method is verified through simulation and experiment.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.1
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• pp.8-18
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• 2002

In this paper, wave energy absorption of OWC(oscillating water column) device is analyzed. The analytic model consists of a partially immersed circular vertical cylinder open at its end and an air turbine connected with the air chamber. The boundary value problem is decomposed into scattering problem related to scattering by an incident wave in the absence of a pressure variation and radiation problem describing the flow due to an oscillating pressure in the absence of an incident wave. By invoking the continuity of an air flow inside the chamber, the oscillating pressure in a chamber is derived. With oscillating pressure, the mean power absorbed by OWC device and the capture width are obtained. In numerical calculation, the induced volume flux across the internal free surface of the chamber in the scattering and radiation problem and the maximum capture width are compared with various design parameters such as radius and submergence depth of chamber and wave conditions. The maximum capture width obtained by choosing the optimal value of turbine constant occurs at the first resonant mode (Helmholtz mode) among the natural frequencies of a circular cylinder chamber.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1377-1383
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• 2014

This paper deals with eddy current loss of magnetic coupling with radial permanent magnet (PM) using analytical method such as a space harmonic method. Superposition of two kinds analysis model is used to analyze eddy current loss induced in inner PM and outer PM of magnetic coupling. When the eddy current is induced, the environmental temperature increases, and the permanent magnet(PM) characteristics are degraded because the performance of PM is greatly influenced by temperature rise. Hence, the calculation of eddy current loss becomes an important factor in the magnetic coupling. In order to analyze eddy current loss, first, on the basis of the magnetic vector potential and two-dimensional(2-D) polar-coordinate system, the magnetic field solutions of the radial magnetized PM are obtained. And we obtain the analytical solutions for the eddy current density produced by permanent magnet. Lastly, analytical solutions for eddy current loss are derived by using equivalent, electrical resistance calculated from magnet volume and analytical solution for eddy current density. This analytical results are validated by comparing with the 2-D finite element analysis (FEA).

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.51-55
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• 2008

Purpose: To develop the program used in calculating and estimating anamorphic prisms used to construct an anamorphoser. Methods: If there is a program which can show the apex angle and the volume of prism which are decided by the refraction index of anamorphic prisms and the expanding ratio of incident beam, the production of anamorphic prisms can be done accurately. Moreover, it could become a convenient tool to the design and production of whole optical systems using anamorphic prisms. Developing this program, first, we had to induce formulas of prism that decide the apex angle and the arrangement angle of anamorphic prisms with the given refraction index of anamorphic prism and the given expanding ratio of incident beam. Then we programmed them by delphi 6.0 language so that they could be visualized on screen and easily confirmed. Results: We could develop the program used in calculating and estimating anamorphic prisms used to construct an anamorphoser. Conclusions: Judging from the results of applying this developed program to actual business, we could conclude that this program is useful in calculation and production of anamorphic prisms which are used as components of an anamorphoser because this program can offer a lot of accuracy and quickness to producers.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.4
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• pp.77-87
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• 1994

This paper deals with an automated forming sequence design system by which designers can determine desirable operation sequences even if they have little experience in the design of cold forging process. The forming sequence design in the cold forging is very important and requires many kinds of technical and empirical knowledge. They system isproposed, which generates forming sequence plans for the multistage cold forging of axisymmtrical solid products. Since the process of metal forming can be considered as a transformation of geometry, treatment of the geometry of the product is a key in planning process. To recognize the geometry of the product section, section entity representation and primitive geometries were used. Section entity representation can be used for the calculation of maximum diameter, maximum height, and volume. Forming sequence for the part can be determined by means of primitive geometries such as cylinder, cone, convex, and concave. By utilizing this geometrical characteristics (diameter, height, and radius), the product geometry is expressed by a list of the priitive geometries. Accordingly the forming sequence design is formulated as the search problem which starts with a billet geometry and finishes with a given product one. Using the developed system, the sequence drawing with all dimensions, which includes the proper sequence of operations for the part, is generated under the environment of AutoCAD. Based on the results of forming sequence, process variables(strain, punch pressure, die inner pressure, and forming load) are determined.

• Journal of Biomedical Engineering Research
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• v.27 no.4
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• pp.189-196
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• 2006

Micro computed tomography (micro-CT) has been used for in vivo animal study owing to its noninvasive and high spatial resolution capability. However, the sizes of existing detectors for micro-CT systems are too small to obtain whole-body images of a small animal object with $\sim$10 micron resolution and a part of its bones or other organs should be extracted. So, we have introduced the zoom-in micro-tomography technique which can obtain high-resolution images of a local region of an live animal object without extracting samples. In order to verify our zoom-in technique, we performed in vivo animal bone study. We prepared some SD (Sprague-Dawley) rats for making osteoporosis models. They were divided into control and ovariectomized groups. Again, the ovariectomized group is divided into two groups fed with normal food and with calcium-free food. And we took 3D tomographic images of their femurs with 20 micron resolution using our zoom-in tomography technique and observed the bone changes for 12 weeks. We selected ROI (region of interest) of a femur image and applied 2D FDT (fuzzy distance transform) to measure the trabecular bone thickness. The measured results showed obvious bone changes and big differences between control and ovariectomized groups. However, we found that the reliability of the measurement depended on the selection of ROI in a bone image for thickness calculation. So, we extended the method to 3D FDT technique. We selected 3D VOI (volume of interest) in the obtained 3D tomographic images and applied 3D FDT algorithm. The results showed that the 3D technique could give more accurate and reliable measurement.